1. Field of the Invention
The present invention relates to a method for inkjet printing method and an image forming apparatus.
2. Description of the Related Art
Printers using an inkjet printing method eject a liquid or melt-solid ink from a nozzle, a slit or a porous film to record on paper, fabric or film, and are known to have advantages such as small size, inexpensiveness and quietness. Furthermore, a piezo inkjet printing method using a piezoelectric element, and a heat inkjet printing method in which recording is carried out by applying heat energy to an ink have been developed aiming at increasing printing velocity and improving resolution of an image.
Although the piezo inkjet printing method and heat inkjet printing method have advantages such as high printing velocity and improved image resolution, they are sometimes disadvantageous in that printing properties deteriorate when plain paper is used as a recording medium, and that feathering when printing in a single color, inter-color bleeding, which is a disadvantage in color printing using multiple colors, curling, where paper curls to the surface on which an image has been printed, or cockling, whereby the paper is deformed to become wavy, may occur depending on the kind of paper. Accordingly, it is difficult to obtain excellent image quality irrespective of the kind of recording medium.
Japanese Patent Application Laid-Open (JP-A) No. 11-188855 suggests an image forming apparatus aiming at improving image quality, specifically in the case where gloss paper is used as a recording medium, by providing powder having a porous structure to an image portion after formation of an image using a recording liquid to prevent the image from contacting other articles.
Although the image forming apparatus using the above-mentioned system can prevent deterioration of image quality due to contact of other articles, such as other recording medium, with the image printed on the recording medium, the apparatus is not formed from the viewpoint of prevention of disadvantages such as the above-mentioned feathering, inter-color bleeding, curling and cockling that may occur on the printed image formed on the recording medium. Accordingly, the apparatus can not essentially or sufficiently improve these disadvantages .
Specifically, when plain paper is used as a recording medium, the above-mentioned image forming apparatus cannot be sufficiently prevented disadvantageous such as feathering, inter-color bleeding, curling and cockling, and therefore excellent image quality can not be obtained by using the apparatus.
In view of this, JP-A No. 2002-178624 suggests a method comprising dispersing a predetermined amount of powder that can separate a colorant and a solvent in an ink to the surface of the recording medium before ejection of the ink, or dispersing a predetermined amount of the powder immediately after dropping of the ink to the surface of the recording medium. In this publication, the “powder that can separate a colorant and a solvent in an ink” units powder that can absorb the solvent in the ink or powder that coagulates the colorant in the ink.
Where the powder that can absorb the solvent in the ink is used, the powder absorbs the solvent in the ink, whereby spreading of the ink dropped on the recording medium in the direction of the surface of the recording medium can be prevented. Where the powder that coagulates the colorant in the ink is used, the colorant coagulates upon contact of the ink with the powder on the recording medium, whereby the components in the solvent other than the ink are absorbed to permeate into the recording medium, whereas the colorant is separated from the solvent components, and remains and coagulates on the surface of the recording medium without being absorbed by the recording medium. Accordingly, feathering, inter-color bleeding, curling and cockling can be prevented by using such powders.
However, the above-mentioned method is disadvantageous in that it is difficult to fix the ink since the ink is provided on the powder, which impairs image fastness. In addition, there also exists a disadvantage that the image concentration easily becomes uneven due to poor fixing of the ink.